1. Technical Field
The present invention relates to a printing apparatus and a printing method.
2. Related Art
An inkjet printing apparatus is an apparatus which performs printing by ejecting ink from a head. The inkjet printing apparatus includes apparatuses such as a printer, a plotter, or a facsimile. Some of these printing apparatuses control operation of elements provided in a head by drive signals and eject ink; wherein an amount of ink is different depending on a tone level (see JP-A-10-193587, for example). The above-mentioned apparatuses perform such control using four tone levels: non-formation of a dot, a small dot, a medium dot, and a large dot. Thus, four-types of drive signals are generated and are applied to elements.
Some of the above-mentioned printing apparatuses eject a plurality of types of inks whose color and color material (dye or pigment) are different. In the printing apparatuses, the types of drive signals applied to elements are the same regardless of the type of ink.
In case of control as mentioned above, there is a problem that graininess deteriorates. It can be considered that the problem is caused because the perceived size of a dot is different depending on the type of ink with which the dot is formed even if an amount of ink used for formation of the dot is the same. For example, in case of a printing apparatus which performs printing by ejecting light ink and dark ink of a same color, a dot formed with light ink tends to be visually perceived larger than a dot formed with dark ink. This tendency becomes more conspicuous at a somewhat high tone level. Therefore, if an amount of ink used for dot-formation is the same between light ink and dark ink, the difference in size between a medium dot and a large dot which are formed with light ink becomes excessively great, for example, and this causes graininess to deteriorate.